The current trend in communications and computer network systems is to provide a broad functionality within an integrated network, capable of handling some or all of voice, text, data, video, and still images. Such systems may also access external or shared resources, (e.g. image databases or video on demand), while allowing for video telephony and collaborative working within the office. Such systems typically use a LAN network within premises and ISDN or similar links to other sites.
Current LAN systems, regardless of topology, generally deliver much less useable bandwidth than is theoretically promised, due to system overheads, compression/decompression at terminals, and other factors. Installation of video capabilities for some or all terminals on an already near capacity LAN is likely to further degrade performance, particularly given the bursty nature and high bandwidth requirements for video. Further, installation of compression/decompression facilities onto terminals requires either very high performance, expensive hardware, or the acceptance of a loss of computation power for other tasks. It is network performance which in current LAN arrangements will provide the ultimate limitation on effective performance.
U.S. Pat. No. 5,170,252 to Gear et al discloses a device for enabling the selective connection of video and audio signals to multiple terminals on a local network. The arrangement disclosed uses a specialised pipeline within the device to carry signals.
It is an object of the present invention to provide an improved arrangement allowing for existing LAN-based systems to cope with video and similar signals, without the need for customised hardware or cabling.